linux-kernel - Re: Re: [PATCH v2] mm: hugetlb: add hwcrp_hugepages to record memory failure on hugetlbfs

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Message-ID: <20210711142001.1780-1-wangbin224@huawei.com>
Date:   Sun, 11 Jul 2021 22:20:01 +0800
From:   Bin Wang <wangbin224@...wei.com>
To:     <naoya.horiguchi@...ux.dev>
CC:     <akpm@...ux-foundation.org>, <linux-kernel@...r.kernel.org>,
        <linux-mm@...ck.org>, <mike.kravetz@...cle.com>,
        <naoya.horiguchi@....com>, <wangbin224@...wei.com>,
        <wuxu.wu@...wei.com>
Subject: Re: Re: [PATCH v2] mm: hugetlb: add hwcrp_hugepages to record memory failure on hugetlbfs

Hi Naoya,

> > Yes, splitting the huge pages and isolating a base page is ideal. And
> > we do this with dissolve_free_huge_page() when page_mapping() return
> > NULL. I think there is a reason(but I do not get it) why we don't split
> > huge pags in hugetlbfs_error_remove_page() or after. So I choose to 
> > add a new count.
> 
> Maybe the resource is the main reason of this incompleteness, I noticed this
> for years and continued to say "this is in my todo list", but still don't
> make it (really sorry about that...).  Anyway, if you can (I hope) solve
> your problem with "/proc/kpageflag" approach, which is a recommended solution.

I do not understand the exact meaning of the "resource". I have tried to call
dissolve_free_huge_page() after hugetlbfs_error_remove_page() and it worked.
In my opinion, the error huge page has been truncated from the hugetlbfs. It
cannot be accessed and allocated again. I think it is safe to split it.

I would appreciate it if you could point out what I overlooked. And I will
try to solve it.

Thanks,
Bin Wang